A widely employed type of tube bending machine embodies an elongated machine bed at one end of which is mounted apparatus for achieving draw bending or press bending of the tube. A multiple bend tube commonly has a number of bends located at different points along the tube and having the planes of different bends angularly shifted about the tube axis. Other variables in the bending process, whether performed by a draw or press bending, include the degree of bend and the radius of the bend. The latter two variables commonly are handled by the bending head. The position of the bend along the axis of the tube and the angular position of the plane of bend are often handled by a mechanism which grasps the tube and advances it toward the bending head to position the point of bend at the proper location with respect to dies in the bending head. The tube grasping mechanism also rotates the tube relative to the bending head to attain a selected plane of bend. Such tube handling mechanism must be simple, reliable and accurate. It must be lightweight for a fast response time, particularly where a number of bends are to be made in rapid succession by a machine that is entirely automatically controlled. Thus, many bending machines in the past have embodied separate driving mechanisms for carriage travel and chuck rotation. Heavy, expensive, ball screw drives have been employed, and these often are provided in duplicate for the driving of the chuck and the driving of the carriage. In some arrangements, one or more heavy driving motors is carried by the carriage.
Precision ball screw drives for a machine having a typical ten-foot length of travel are massive and expensive. Where motors are mounted on the carriage, not only is the motor cost increased by use of plural motors, but the carriage and all supporting and driving structures must be stronger, heavier, more expensive, and more difficult to precisely and rapidly control. In some prior arrangements, one motor has been employed for two drives, but these have still required duplication of the driving connection between the motor and the several driven members.
Accordingly, it is an object of the present invention to provide a common drive for several driven members which eliminates or minimizes the above-described disadvantages.